In the manufacture of glass fibers either in a marble melt bushing or by the direct melt process molten glass fibers are drawn from the bottom of a bushing having a plurality of orifices therein. The bushings are constructed of a material resistant to attack by the molten glass contained in them, typically platinum or a platinum-rhodium alloy. In the marble melt bushings glass marbles of suitable composition for the preparation of glass filaments are fed to the upper portion of an electrically heated bushing and the molten glass located in the bottom of the bushing which has been rendered molten by the heating of the glass marbles as they pass through the bushings are drawn through a plurality of orifices or tips located at the bottom of the bushing and collected by winding, chopping or various other secondary procedures. In a direct melt operation, loose glass batch is melted in large quantities in a glass furnace and fed to a forehearth from which a multiplicity of bushings depend and through which the molten glass flows. Thus, the molten glass flows from the furnace through the forehearth and into the bushings. The bushings are again electrically controlled to maintain melting temperatures in the range of 2,000.degree. to 2,400.degree. F. (1090.degree. to 1310.degree. C.) or greater.
In applying and maintaining glass melting temperatures to a bushing proper through electrical heaters provided in the bushing in either of the processes described, considerable stress is placed upon the bushing due to expansion of bushing, the heating elements and the connectors located on the sides of the bushings which deliver current to the bushing. Electrical power is supplied to the bushing normally through two bushing terminals located on either side of the bushing and through two buss bars which are electrically connected to the bushing terminals at one end and connected to the secondary of a power transformer at the other end. Between the connectors to the bushing terminal and the transformer terminal copper buss bars are utilized which normally take the form of braided copper flexible rope or more frequently of flexible copper sheets which are leaved together and mechanically bonded at each end to a connector which is adapted to be connected to the bushing terminal at one end and the transformer secondary at the other end. Flexible copper sheets and flexible braided copper wire are utilized in the application so that thermal stresses and mechanical stresses on the bushing and its connectors can be relieved by the ability of the buss bar itself to flex during operation while the bushing is being heated.
In these prior art buss bar connections, the buss bar utilized to carry currents to the bushing, currents being typically 3,000 to 4,000 amperes at 3 to 7.5 volts, are quite cumbersome and heavy and in a typical bushing can reach weights with their terminal connectors added in of 16 pounds or more. The weight of the buss bar and the terminal connectors utilized to clamp the buss bar to the bushing terminal and the transformer secondary add considerable stress to the bushing. Thus, because of this weight coupled with the thermal expansion of the bushing as it is heated to these elevated temperatures i.e. temperatures of 2,000.degree. F. or above, considerable mechanical stress is placed on the bushing which causes bushing failures in many instances and especially at the terminal connector points on the bushing, generally referred to in the art as the "bushing ears." Further in connecting the buss bars to the bushing terminal and the transformer terminal it is common practice to employ bolts in the bushing terminal area to firmly affix the buss bar to the bushing ear. A typical illustration of the connections of a buss bar to a transformer and to a bushing terminal is shown in FIGS. 3 and 5 of U.S. Pat. No. 4,003,720. Because the connection at the bushing terminal to the buss bar is through a bolted connection, should it be desirable, as it often is in operating the bushing, to move the buss bar closer to the bushing wall or farther away from the bushing wall than its original operating location, all of the bolts must be loosened to move the connector and the buss bar in the desired manner. This is often quite difficult to accomplish because of the atmosphere prevailing around the bushing which causes water and binder deposits on the equipment rendering the loosening of the bolts difficult.
Thus there is a need for providing a bushing terminal and buss bar assembly which is simpler in operation than those presently available in the art, which will render the bushing terminal and buss bar less cumbersome in weight thereby reducing substantially the stresses placed upon the bushing ears to which the bushing terminal and buss bar are connected, and to provide a bushing terminal connection system which will allow for rapid adjustment of the bushing terminal with respect to the bushing heating element with a minimum of time and effort. It is also desirable in constructing bushing terminals and buss bars to eliminate, if possible, the need for the large quantities of electrically conductive material, and copper in particular, currently utilized in the industry to make these connections.